: The transcriptional control of viral gene expression is strongly influenced by the interaction of host transcription factors and a virus promoter element. The promoter from rice tungro bacilliform badnavirus (RTBV) accounts for the tissue-specific replication of the virus. Two bZIP proteins, RF2a and RF2b, were isolated from rice. These proteins bind to the viral promoter and can fonn homodimers and a heterodimer. The proposed research analyzes the structure and the interaction of the two proteins using computational modeling. The accuracy of the prediction from the models will be tested by biochemical methods followed by functional analysis to correlate the protein-protein interaction with function. The experimental data will be used as feedback to the modeling to obtain more accurate structure prediction. The proposed research should allow better understanding of the control of RTBV promoter expression.